1. Log-in to Office 365 using the script below:

$UserCredential = Get-Credential

$Session = New-PSSession –ConfigurationName Microsoft.Exchange –ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $UserCredential –Authentication Basic -AllowRedirection

Import-PSSession $Session

2. Once signed-in use the command below to select and convert the desired account to Shared:

Set-Mailbox yourmailboxusername@yourdomain.com -Type shared

3. Verify the mailbox has Shared status.

Get-Mailbox -Identity yourmailboxusername@yourdomain.com | Format-List RecipientTypeDetails

4. Sign-out of Office 365.

Remove-PSSession $Session